This patent application claims priority from a Japanese patent application No. 2002-306270 filed on Oct. 21, 2002, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an electron beam exposure apparatus and a deflection amount compensation method. More particularly, the present invention relates to an electron beam exposure apparatus and a deflection amount correction method for controlling deflection amount of an electron beam based on a position of a wafer stage.
2. Description of Related Art
In a conventional electron beam exposure apparatus, after the wafer stage is driven for specifying the position at which an electron beam is to be applied on the wafer, the wafer stage has to be stopped during the exposure processing. However, according to the above-mentioned method, it takes some times to start and stop the wafer stage, and consequently it takes a lot of time to perform the exposure processing. To solve the problem, a Japanese Patent Unexamined Publication No. 1987-277724 discloses an electron beam exposure system for exposing a wafer mounted on the continuously moving wafer stage by periodically measuring the position of the wafer stage during the exposure processing, and controlling deflectors and driving the wafer stage continuously in accordance with the measurement result.
Recently, semiconductor devices have been highly miniaturized. Therefore, it is required to improve exposure precision of the exposure apparatus for writing pattern of semiconductor devices. Moreover, demand for mass production of the semiconductor devices is increasing and it is also required to improve throughput of the exposure apparatus. As the result, there is a tendency for moving speed of the wafer stage to increase, which causes deterioration of the exposure accuracy.
Therefore, it is an object of the present invention to provide an electron beam exposure apparatus and a deflection amount compensation method which can solve the foregoing problem. The above and other objects can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.
According to a first aspect of the present invention, there is provided an electron beam exposure apparatus for exposing a pattern on a wafer by an electron beam. The electron beam exposure apparatus includes: an electron beam generating section for generating the electron beam; a deflecting section for deflecting the electron beam in order to apply the electron beam to a desired position on the wafer; a wafer stage on which the wafer is mounted; a stage position measuring section for measuring position of the wafer stage at a first time point and at a second time point which is later than the first time point; a stage speed computing section for computing moving speed of the wafer stage based on the position of the wafer stage at the first time point and the position of the wafer stage at the second time point, which are measured by the stage position measuring section; and a deflection amount correction section for computing position of the wafer stage at exposure time based on the moving speed of the wafer stage measured by the stage speed computing section, and for controlling deflection amount of the electron beam to be deflected by the deflecting section at the exposure time.
The stage speed computing section may include: a first stage position storage section storing thereon the position of the wafer stage at the first time point; a second stage position storage section storing thereon the position of the wafer stage at the second time point; and a gradient computing section for computing the moving speed of the wafer stage based on the position of the wafer stage at the first time point stored on the first stage position storage section and the position of the wafer stage at the second time point stored on the second stage position storage section. The deflection amount correction section may include: a first deflection data generating section for generating a first deflection data, which is to be supplied to the deflecting section, based on the position of the wafer stage at the second time point stored on the second stage position storage section; and a second deflection data generating section for generating a second deflection data indicating the deflection amount corresponding to the moving distance of the wafer stage during a time interval between the second time point and the exposure time based on the moving speed of the wafer stage computed by the gradient computing section. The deflection amount correction section may supply the first deflection data and the second deflection data to the deflecting section.
The deflection amount correction section may further include an adding section for adding the first deflection data and the second deflection data, and supplying the added data to the deflecting section. The deflecting section may include: a first deflector for deflecting the electron beam based on the first deflection data; and a second deflector for deflecting the electron beam based on the second deflection data. The deflection amount correction section may supply the first deflection data to the first deflector, and supply the second deflection data to the second deflector.
The second deflection data generating section may compute the moving distance of the wafer stage during a time interval between the second time point and the exposure time by accumulating the moving distance per unit time whenever the unit time is elapsed, the moving distance per unit time being computed by the gradient computing section based on the moving speed of the wafer stage, and the unit time being shorter than the time interval between the first time point and the second time point, and then the second deflection data generating section generates the second deflection data indicating the deflection amount corresponding to the moving distance of the wafer stage during the time interval between the second time point and the exposure time.
The second deflection data generating section may compute the moving distance of the wafer stage during the time interval between the second time point and the exposure time by accumulating the moving distance per unit time whenever the unit time is elapsed after the second deflection data is initialized synchronizing with generation of the first deflection data by the first deflection data generating section.
The stage position measuring section may measure position of the wafer stage at a predetermined time interval, the first stage position storage section and the second stage position storage section may update the position of the wafer stage to store whenever the stage position measuring section measures the position of the wafer stage, the first deflection data generating section may acquire exposure data including information indicating the exposure position on the wafer, and generate the first deflection data based on the position of the wafer stage stored on the second stage position storage section when the exposure data are acquired, and the gradient computing section may compute the moving speed of the wafer stage based on the position of the wafer stage stored on the first stage position storage section and the second stage position storage section when the first deflection data generating section acquires the exposure data.
According to a second aspect of the present invention, there is provided an electron beam irradiation apparatus for irradiating an electron beam to a predetermined position in an object. The electron beam irradiation apparatus includes: an electron beam generating section for generating the electron beam; a deflecting section for deflecting the electron beam in order to apply the electron beam to a desired position on the object; a stage on which the object is mounted; a stage position measuring section for measuring position of the stage at a first time point and at a second time point which is later than the first time point; a stage speed computing section for computing moving speed of the stage based on the position of the stage at the first time point and the position of the stage at the second time point, which are measured by the stage position measuring section; and a deflection amount correction section for computing position of the stage at exposure time based on the moving speed of the stage measured by the stage speed computing section, and for controlling deflection amount of the electron beam to be deflected by the deflecting section at the exposure time.
According to a third aspect of the present invention, there is provided a deflection amount correction method for correcting deflection amount of an electron beam deflected by a deflecting section based on position of a wafer stage on which a wafer is mounted in an electron beam exposure apparatus for exposing a pattern on the wafer by the electron beam. The deflection amount correction method includes steps of: measuring position of the wafer stage at a first time point and at a second time point which is later than the first time point; computing moving speed of the wafer stage based on the position of the wafer stage at the first time point and the position of the wafer stage at the second time point; and computing position of the wafer stage at exposure time based on the moving speed of the wafer stage, and controlling deflection amount of the electron beam at the exposure time.
The summary of the invention does not necessarily describe all necessary features of the present invention. The present invention may also be a sub-combination of the features described above.